This invention relates generally to an improved total knee arthroplasty, including a symmetric femoral prosthesis adapted for implantation into either the left or right leg of a patient. More particularly, this symmetric femoral prosthesis has an anterior flange with an upwardly diverging anterior and symmetric or double Q-angle trochlear groove formed therein to accommodate natural tracking of a natural or prosthetic patella as the knee is moved normally between a substantially fully flexed and a substantially fully extending position.
Total knee arthroplasties are generally known in the art, wherein the articulating surfaces of the knee joint are replaced by a femoral component adapted for affixation onto the lower end of a resected patient femur, and a tibial component adapted for affixation onto the upper end of a resected tibia. In a typical design, a bearing insert constructed from a biocompatible and relatively high density plastic material such as a high density polyethylene or the like is fitted onto the tibial component and defines a pair of concave depressions for seated articulation of a matching pair of arched or convexly shaped condyles defined at the lower end of the femoral component. Such knee prostheses are used upon failure of the natural anatomical structures of a patient's knee joint, due to injury or disease.
A residual problem remains, however, involving tracking of the natural or a prosthetic patella (knee cap) against the knee prosthesis, typically an anterior surface of the femoral component. More particularly, the patella normally tracks through an upwardly diverging so-called Q-angle ranging from about 0° when the knee joint is fully flexed to a lateral or laterally outboard angle of about 10° when the knee joint is fully extended. In other words, flexion of the knee decreases the Q-angle, whereas extension of the leg increases the Q-angle; this phenomenon is believed to be due to internal rotation of the tibia. Clearly, the lateral direction for the patient's left knee joint is opposite to the lateral direction for the patient's right knee joint.
In the past, anatomical tracking of the patella against the prosthetic femoral component has generally entailed the use of different femoral components for the patient's left knee vs. the right knee, wherein each femoral component has a so-called trochlear groove extending from the lower to the upper margins of the femoral component at a specified constant-width angle (typically about 6-9° or 5-10° from a vertical direction) for correct patella tracking. However, such use of different left vs. right femoral components undesirably increases the total knee arthroplasty production cost. Attempts to provide a single femoral component having a wider constant width dimension suitable for correct patella tracking irrespective of the left vs. right knee joint of the patient have resulted in poor overall patella tracking and associated patient discomfort when implanted into a patient.
There exists, therefore, a significant need for further improvements in and to the femoral prosthesis or femoral component of a total knee arthroplasty wherein the improved femoral component accommodates accurate anatomical tracking of a natural or prosthetic patella irrespective of the specific left or right knee joint of the patient into which the prosthesis is implanted. The present invention fulfills these needs and provides further related advantages.